C250 (W204) 2011 - 722.9 Gearbox or wiring?

[DCDw163w204]

Hi Everyone,

I have read so many threads about 722.9 Gearbox issues, but none have helped me diagnose what is really going on. I suspect it is not mechanical but I think a gearbox oil change is long overdue, more on this later...

So over the last 3 months, particularly after longer drives the car has when still warm failed to start. Normally a few resets and turns of the key all is well again. I did not notice whether at the same time the gear selector on the dash lost information on what gear and stopped the car starting? Gear shifts have always been smooth apart from a few very cold mornings when as this problem got worse when the car started it would not go into gear until things had warmed up. The first selection D or R was very clunky. Once warm no problems.

The problem was getting worse and about 3 weeks ago it will only occasionally turn over and start, but selecting D or R and the car went nowhere.

The codes I get are as follows: (29 Jan)
U010187 Current and Historic: Transmission has a malfunction message is missing.
U000288 Historic: Drive train CANBUS off, FaultBUS off.
U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

I had some others on the 8 Feb but think they were red herrings, although may have been present after car refused to go to my local bar:
124000 Canbus,
C1000 comms with ECU mal func.
C11100 Comms with battery mal func.
C15500 comms with instrument cluster mal func.
C16800 Comms with ignition switch mal func.

Some other faults which were associated with a faulty wheel sensor that cleared when I replaced the sensor. I bought a gearbox service kit - a Mercedes dealer in France charged me twice as much as a UK dealer!!!

I have not carried out the transmission service yet.

Any ideas and or help finding relevant wiring diagrams or information gratefully accepted.

David

 

[DCDw163w204]

Hi Everyone,

I have read so many threads about 722.9 Gearbox issues, but none have helped me diagnose what is really going on. I suspect it is not mechanical but I think a gearbox oil change is long overdue, more on this later...

So over the last 3 months, particularly after longer drives the car has when still warm failed to start. Normally a few resets and turns of the key all is well again. I did not notice whether at the same time the gear selector on the dash lost information on what gear and stopped the car starting? Gear shifts have always been smooth apart from a few very cold mornings when as this problem got worse when the car started it would not go into gear until things had warmed up. The first selection D or R was very clunky. Once warm no problems.

The problem was getting worse and about 3 weeks ago it will only occasionally turn over and start, but selecting D or R and the car went nowhere.

The codes I get are as follows: (29 Jan)
U010187 Current and Historic: Transmission has a malfunction message is missing.
U000288 Historic: Drive train CANBUS off, FaultBUS off.
U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

I had some others on the 8 Feb but think they were red herrings, although may have been present after car refused to go to my local bar:
124000 Canbus,
C1000 comms with ECU mal func.
C11100 Comms with battery mal func.
C15500 comms with instrument cluster mal func.
C16800 Comms with ignition switch mal func.

Some other faults which were associated with a faulty wheel sensor that cleared when I replaced the sensor. I bought a gearbox service kit - a Mercedes dealer in France charged me twice as much as a UK dealer!!!

I have not carried out the transmission service yet.

Any ideas and or help finding relevant wiring diagrams or information gratefully accepted.

David

Should of added now, when you turn the key the normal gear selection shows for about 5 seconds then it shows no information, when you turn the key a number of times it tries to turn over short burst. I am currently charging my booster - the battery is less than 3 months old.

 

[alexanderfoti]

This:

U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

Is a giveaway that its a control unti fault.

Checksum is something an embedded computer does to ensure its brain isnt faulty.

It has a stored value for a caulcation (EG 1+5 equals 6).

It then does this calculation on its CPU, IF the answer is not the same, something is wrong. Sometimes you check a checksum fault with no symptoms, but in your case you do.

I have had this fault when the plug isnt secure on the ECU correctly, as there isnt enough power for the electronics to function properly.

 

[toteimerced]

Cheapest thing to do, will be a service and transmission reset, then see what happens.

 

[alexanderfoti]

IMHO that's a waste of money.

 

[W1ghty]

Hi Everyone,

I have read so many threads about 722.9 Gearbox issues, but none have helped me diagnose what is really going on. I suspect it is not mechanical but I think a gearbox oil change is long overdue, more on this later...

So over the last 3 months, particularly after longer drives the car has when still warm failed to start. Normally a few resets and turns of the key all is well again. I did not notice whether at the same time the gear selector on the dash lost information on what gear and stopped the car starting? Gear shifts have always been smooth apart from a few very cold mornings when as this problem got worse when the car started it would not go into gear until things had warmed up. The first selection D or R was very clunky. Once warm no problems.

The problem was getting worse and about 3 weeks ago it will only occasionally turn over and start, but selecting D or R and the car went nowhere.

The codes I get are as follows: (29 Jan)
U010187 Current and Historic: Transmission has a malfunction message is missing.
U000288 Historic: Drive train CANBUS off, FaultBUS off.
U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

I had some others on the 8 Feb but think they were red herrings, although may have been present after car refused to go to my local bar:
124000 Canbus,
C1000 comms with ECU mal func.
C11100 Comms with battery mal func.
C15500 comms with instrument cluster mal func.
C16800 Comms with ignition switch mal func.

Some other faults which were associated with a faulty wheel sensor that cleared when I replaced the sensor. I bought a gearbox service kit - a Mercedes dealer in France charged me twice as much as a UK dealer!!!

I have not carried out the transmission service yet.

Any ideas and or help finding relevant wiring diagrams or information gratefully accepted.

David

MBS Southampton is an MB specialist if you need a recommendation.

 

[DCDw163w204]

Thanks everyone, for your comments. Although my home is Lymington I am now living - most of the time in France and the car is now stuck here with me. Although I have loved this car, since I bought it in 2016 it has always had some odd issues with kickdown causing orange light and power loss. To cut a long story short, we just drove carefully avoiding kickdown after spending money on simpler lower cost solutions. This said, we hit the road and the car has now done 250k miles. It doesn't owe us anything. So I am not going to spend (nor can I afford to) big money on him. So, I will now check in with your individual comments, thanks Guys!

 

[DCDw163w204]

This:

U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

Is a giveaway that its a control unti fault.

Checksum is something an embedded computer does to ensure its brain isnt faulty.

It has a stored value for a caulcation (EG 1+5 equals 6).

It then does this calculation on its CPU, IF the answer is not the same, something is wrong. Sometimes you check a checksum fault with no symptoms, but in your case you do.

I have had this fault when the plug isnt secure on the ECU correctly, as there isnt enough power for the electronics to function properly.

Funny, you mention ECU, I did a basic check on the wiring and plugs, the left hand plug was not seated properly and still is not right but I will look more closely over the next few days. There is slight brading damage on the loom at the rear of the engine but this does not seem to have affected any insulation only the outer brade. I checked the only plug I could see going into the gearbox, slight oil misting but did not seem serious - The belly pan under the gearbox area shows sign of hot oil around the front of the gearbox but not serious. Do you know where I can find a wiring diagram?

 

[DCDw163w204]

IMHO that's a waste of money.

What's IMHO?

 

[DCDw163w204]

Cheapest thing to do, will be a service and transmission reset, then see what happens.

Thanks - I have the service kit but what's a transmission reset - if its what I think it is it only resets the learnt / adapted driving style?

 

[DCDw163w204]

This:

U040283 Historic: Implausible data received from Control Unit Transmission. The Checksum has an incorrect value.

Is a giveaway that its a control unti fault.

Checksum is something an embedded computer does to ensure its brain isnt faulty.

It has a stored value for a caulcation (EG 1+5 equals 6).

It then does this calculation on its CPU, IF the answer is not the same, something is wrong. Sometimes you check a checksum fault with no symptoms, but in your case you do.

I have had this fault when the plug isnt secure on the ECU correctly, as there isnt enough power for the electronics to function properly.

Tend to agree, but was also hoping could be plugs or cabling - you guys have vastly more experience than me and I wondered if plugs and cabling issues were more or much more common than TCU failure? Also was hoping to find a member who had the same issues and had that eureka moment! Such is life. Thanks again.

 

[tony gee]

What's IMHO?

In My Honest Opinion.
a gearbox service is no guarantee it'll fix things but it might be worth fitting a conductor plate while you are at it ???????

 

[toteimerced]

You could give these people a try if necessary, prices are reasonable.

 

[DCDw163w204]

In My Honest Opinion.
a gearbox service is no guarantee it'll fix things but it might be worth fitting a conductor plate while you are at it ???????

Thanks, yes, over the week end I will start the service and pull out the conductor plate.